Earliest process of water radiolysis at the electron track end

Kai, Takeshi   ; Yokoya, Akinari*; Ukai, Masatoshi*; Fujii, Kentaro*; Watanabe, Ritsuko*; Yonetani, Yoshiteru*; Toigawa, Tomohiro   ; Sato, Tatsuhiko   

It is very important to study water radiolysis by electrons because the study are applied to fields involved in atomic industry and radiotherapy, the study is also useful to predict radiation damage to DNA in a living cell. In this study, we calculated deceleration process of secondary electrons produced by ionization at a primary electron track end, at which a primary and secondary electrons densely deposit those energies to water, to understand the earliest process of water radiolysis. From the results, the secondary electrons distributed 10 nm from parent cations at 300 fs, and the mean energy of the electrons reached 0.7 eV. At this timescale, we indicated that the energy distribution shows the non-equilibrium state strongly, and fraction of the electrons energy below 0.1 eV is more than 10. The results may indicate a new insight of the formation of prehydrated electrons due to the extremely low energy electrons.